Shooting Game I

Review — the Car Race, finished 5 min

• A broadcast says where to go; a variable says what was chosen.
• Give every setting a default before the player sees anything.
• A My Block is worth making even with no inputs.
• Clones let one sprite be in many places at once.

Quick-fire

You have one sprite and you need twenty of them on screen at once. What do you reach for?

Today’s Topic 3 min

• Planning a game before building it
• Aiming with the mouse
• A bullet that knows where it is going
• Enemies that keep coming

Learning outcome

By the end of this lesson you will be able to:

1. Make a sprite face the mouse pointer.
2. Fire a clone that travels in a straight line and cleans itself up.
3. Spawn enemies at random and remove them when they are hit.

Learnt — a game you aim 28 min

The rules, before the blocks

You have built two games now. Both times, deciding the rules first made the building easier. So here are ours:

1. You move with the arrow keys.
2. Your aim always follows the mouse.
3. Click to shoot. The bullet goes where the aim was pointing.
4. Enemies come from the left, at random, for ever.

That is all. Four rules is a game. Everything after that is polish.

Aiming with the mouse

Two sprites, two blocks. A crosshair that sits on the pointer, and a player that turns to face it.

when flag clicked
go to [front v] layer
forever
  go to [mouse-pointer v]
end
            

set rotation style [left-right v]
forever
  point towards [mouse-pointer v]
end
            

Firing a bullet

When the mouse goes down, the player makes a clone of the Bullet sprite:

when flag clicked
forever
  wait until <mouse down?>
  create clone of [Bullet v]
  wait until <not <mouse down?>>
end
            

And the clone puts itself in the right place and points itself the right way:

when I start as a clone
go to [Player v]
point towards [mouse-pointer v]
go to [front v] layer
show
repeat until <(x position) > (235)>
  move (7) steps
end
delete this clone
            

Enemies that keep coming

One sprite does all of them. The original never appears — it just makes clones:

when flag clicked
hide
forever
  wait (pick random (0.8) to (2.5)) seconds
  go to x: (-210) y: (pick random (-140) to (140))
  create clone of [myself v]
end
            

when I start as a clone
show
repeat until <(x position) > (225)>
  change x by (1.6)
  if <touching [Bullet v]?> then
    change [score v] by (1)
    delete this clone
  end
end
delete this clone
            

Basic — the first draft 24 min

New project. Four sprites: Player, Aim, Bullet, Zombie.

Step 1 — draw quickly

Top-down is easiest: a circle with something sticking out for the player, a blob for the enemy, a small dot for the bullet, a cross for the aim. Five minutes, not fifty.

Step 2 — the aim

A forever loop with go to [mouse-pointer v] inside it, and go to [front v] layer so it is never hidden behind anything.

Step 3 — the player

The movement loop from Lesson 6, with change x by (px) and change y by (py) instead of move (10) steps. Then point towards [mouse-pointer v] at the bottom.

Step 4 — shooting

The player’s second stack, and the Bullet’s clone script.

Step 5 — the enemies

The spawner and the walker.

Step 6 — hitting

Add the touching [Bullet v]? check to the enemy, and a matching touching [Zombie v]? to the bullet so it does not fly on through.

Step 7 — play it

Two minutes without stopping. Write down anything that felt wrong.

Move and aim

• Arrow keys move the player, with weight — it slides to a stop.
• The crosshair follows the mouse everywhere.
• The player always faces the mouse.
• The player cannot leave the Stage.

Shooting

• One click, one bullet.
• The bullet starts at the player and goes where you were aiming.
• It disappears when it leaves the Stage.
• Holding the button down does not machine-gun.

Hold the line

The deck’s mission: the first playable draft.

• Enemies arrive from the left at random times and random heights.
• They walk across and disappear at the far side.
• A bullet stops one, and your score goes up.
• It can be played for two minutes without slowing down.

Design it properly

The deck asks you to draft your game and write the rules down before you build any more. Do that — and make it your game, not ours.

• What is the player, and what is chasing them?
• How do you lose?
• Is there a way to win, or does it go for ever?
• What gets harder as you go?

Summary 5 min

• Write the rules before the blocks. Four rules is a game.
• go to [mouse-pointer v] and point towards [mouse-pointer v] are all an aim needs.
• point towards [mouse-pointer v] runs once. After that a bullet cannot be steered.
• A when I receive [Fire v] hat runs on every clone — which is why the player, not the bullet, makes the clone.
• Never spawn a sprite on the edge if you are going to ask whether it is touching one.

Aim

A sprite that shows where you are pointing.

Spawn

To make a new enemy appear.

Wave

Enemies arriving one after another.

Draft

The first version that plays. Ugly is fine.

Hand in

Share your draft and send the link to your teacher, with your five rules. Next lesson the enemies fight back.